Process of treating nitric acid by electrolysis.



"rrrm s'rap'rns jPATEN'r OFFICE.

MARTIN MOEST AND RUDOLF IZEllLLER VON BERNECK, 0F HCHST-ON-THE-MAIN, GER- MANY, Assrenoias T0 HoCHsr-oN-THEMAIN,

FARBNERKE VORM. MEISTER LUCIUS & BRIINING, OF GERMANY A CORPDRATION OF GERMANY.

PROCESS OF TREATING NITRIC ACID BY ELECTROLYSIS.

Specification of Letters Patent.

No Drawing. Application filed July 26,

To all whom it may concern:

Be it known that we, MARTIN Moi-1ST,

Ph. 1)., chemist, and ItUnoLr Mi'frnnnn VON lulmnen, chemist, citizens of the Empire of Germany, residing at I-lochst-on-the-Main, Germany, have invented certain new and useful Improvements in the Process of Treating Nitric Acid by Electrolysis, of which the following is a specification.

In the processes or" treating nitric acid by electrolysis .in the cathode-compartment of an electrolytic cell without adding other electrolytes, there have hitherto been used only metallic electrodes, generally platinum, in special cases copper, mercury or the like. Now, we have made the observation that these metals can be advantageously replaced in most cases by carbon or graphite electrodes. We have found that carbon or graphite as cathodes are absolutely stable in nitric acid. This observation is most surprising in view of the fact that carbon or graphite when used as anodes in nitric acid are destroyed in a very short time, and must also be regarded otherwise as unstable against the action of nitric acid. (Compare Danimer Handbook, 1894, vol. II, art 1, page 62.) Thus, in the process described in German Patent No. 180052 there may be used a carbon or graphite electrode in the place of the platinum electrode without es-. sentially altering the results. Now, as carbon is much chea er than platinum, a considerable technica advance is attained by F the said invention.

When using ilatinum electrodes in the electrolysis of diluted nitric acid, for instance of a strength of about 20-30 per cent, in the cathode-compartment there 00-. curs an evolution of hydrogen at the beginning of the electrolysis or on continuin the test, even after a short interruption o? the current, and there is always some time required until the normal course of the process is attained, which consists principally in the reduction of nitric acid to ammonia. Sinn- Schiinbein (Poggcndor s Annalcn, 1839, vol. 47, page 563.) This evolution of by drogen at the caused by its easily becoming passive, is very dangerous for technical purposes, because the gaseous compounds of nitrogen and oxygen which may escape simultaneously, or the access of air in the gas outlets are capable of easily producing an explosive mixture of gases. However by using 111 the place of platinum cathodes, carbon or graphite cathodes and an anode of solving in nitric acid,-the diluted nitric acid is chiefly reduced into ammonia, whil'e' hydrogen is not ewlvcd. Moreover the required voltage of the current is lower. Furthermore carbon or graphite cathodes show great technical advantages over those made of metals. In the electrolysis of diluted nitric acid with aluminiumcathodes ammoniu, for instance, forms, but the aluminium-electrode is thereby sensibly attacked and it requires a very high tension. Carbon or graphite used as cathode, give chemically the same result, namely ammonia with a yield of the current of about 60%. However carbon has the advantage over aluminium of being absolutely stable; moreover the required tension and course quently the consumption of energy is much lower. Under otherwise the same condi- .tions the voltage has been for instance:

Withscurreutdensityof.......l.. ..-1.6 6.5 0 am Thedeniltytor aluminlumuu cathode... 2.0 4.2 5.8 vol u carbon 1.0 8.4

Copper and mercury, which were occasionally used in laboratory tests as cathodes in the electrolysis of nitric acid, do not, technically, enter into consideration at all, as they are, as is known, unstable against the action of nitric acid and undergo in combination with it reaction ,while forming nitric oxid gases.

Having now described 0' we claim is:

r in vention, what lar observations have already been made by l 1. The process of electrolyzing nitric acid.

platinum cathode, which is platinum or of any other material not dis- 6C @I I mmiwgf which consists in passmg an elecmccmi'enfi; Elm-testimony whereof, we afix our slgnatlu'uu h; an electrolyte of nifix'ic acid- 530 a tures in' presence of two witnesses.

3.7916110 eiof carbon. MARTIN HOEBT. 2. The PIOQeSS of electrolyzmg mtrie mud, RUDOLE MfiLLEB, am BERNEGK 5 which consists in pa ssingan electric current Witnesses:

through gn-lcisrolyte of nifii'iiz acid to 3 I JEAN GRUND; aathode of graphite, CABL Gamma, 

